The present invention relates to a cooling device and a counterbalanced forklift. More specifically, the present invention pertains to a cooling device for a control unit used in an industrial vehicle, such as a battery-powered forklift, and a counterbalanced forklift that has the cooling device.
A typical industrial vehicle, such as a battery-powered forklift, has a motor for carrying a load and a motor for driving the forklift. A control unit for controlling the motors is cooled inside the vehicle body.
FIG. 19 shows a prior art cooling device. In the prior art cooling device, cooling fins 101 are arranged on the outer surface of a control unit 100. The cooling fins 101 are covered with a duct cover 102. A cooling fan 103 is attached to one of the openings of the duct cover 102 and draws air into the duct cover 102. The heat generated by the control unit 100 is transmitted to the cooling fins 101 and then released by air drawn into the duct cover 102.
A cooling device, which is shown in FIGS. 20(a) and 20(b), is disclosed in Japanese Laid-open Patent Publication No. 2000-44195 as another cooling method. According to the cooling device of the above publication, a control unit 104 is secured to the outer surface of a battery case 105 with an aluminum base 106 located in between. The aluminum base 106 has a U-shaped groove 106a. A suction pipe 107 for hydraulic oil is inserted through the U-shaped groove 106a. The heat generated by the control unit 104 is transmitted to the aluminum base 106 and then released from the aluminum base 106 by low-temperature hydraulic oil, which flows through the suction pipe 107.
In accordance with the recent development of large battery-powered forklifts and high-powered electric motors, control units tend to be enlarged. That is, in an electric circuit of such control unit, substrates are fixed on a cooling plate, which has a cooling system, in layers. An electric power microchip of, for example, a FET transistor is directly mounted on the cooling plate such that the microchip is effectively cooled. Even though the control unit is cooled via the cooling plate as described above, the electric circuit may not be sufficiently cooled.